Alkanolamines and alkyleneamines are currently manufactured using alkylene oxides and ammonia as the key starting raw materials. For example, monoethanolamine, di- and tri-ethanolamine and ethylenediamine are currently manufactured using ethylene oxide and ammonia as the starting raw materials. The manufacture of monoethanolamine requires high ammonia to ethylene oxide ratios in order to increase the selectivity to monoethanolamine. It is then necessary to refine and recycle the excess ammonia which significantly increases the cost of monoethanolamine production. Once monoethanolamine is formed, it is treated with ammonia by a reductive amination process to produce ethylenediamine and other higher acyclic and cyclic polyethyleneamines. Again, high ammonia ratios are employed to improve the selectivity to the desired end product, typically, ethylenediamine.
Ethylene oxide is a relatively expensive compound, and the high cost of this material also unfavorably impacts the economics of monoethanolamine and ethylenediamine manufacture. In the case of monoethanolamine, for example, the raw materials may account for at least 70% of the total monoethanolamine cost.
Another commercial process utilizes ethylene dichloride and ammonia for the synthesis of ethylenediamine and other higher homologs. This process is energy intensive and requires expensive refining equipment. Furthermore, the resultant hydrochloride salts of ammonia and the polyethyleneamines must undergo neutralization with caustic (usually sodium hydroxide) to give the free amine product. Separation of the polyethyleneamines and the salt is difficult, and the byproduct salt must be disposed of which further increases the cost of the process.
A process which could produce alkanolamines and alkyleneamines from alkanes and/or alkenes as the starting hydrocarbon raw materials would provide a desirable advantage over the current prior art. In the case of monoethanolamine and ethylenediamine, for example, using ethane and/or ethylene as the starting raw material(s) would provide significantly improved variable costs compared to ethylene oxide and ethylene dichloride. It would also avoid the need to handle ethylene oxide--a highly reactive chemical.
The partial oxidative amination of alkanes and alkenes provides a thermodynamically favorable route to alkanolamines and alkyleneamines, as demonstrated further below. The primary concern with respect to the partial oxidative amination of alkanes and alkenes is selectivity, i.e., the formation of desirable alkanolamines and alkyleneamines rather than the complete conversion of the starting materials to CO.sub.2 and water. In addition, preventing or limiting the oxidation of ammonia and other nitrogen sources to NO.sub.x, type species and limiting NO.sub.x /hydrocarbon reactions are other significant concerns.
A process that effectively addresses these concerns would achieve a novel and practicable means of producing alkanolamines and alkyleneamines. Such an approach would also provide clear economic advantages over the present method of synthesizing these materials from ethylene oxide or ethylene dichloride.